In some conventional internal combustion engines, an operating state and/or values of variables important for the operation may be monitored with the aid of a so-called on board diagnosis. Among other things, a correctly set fuel pressure in a pressure accumulator of a fuel system of the internal combustion engine is important. The fuel pressure is frequently ascertained with the aid of a pressure sensor (“rail pressure sensor,” RPS). In order to check or monitor the pressure sensor for proper functioning, it is, for example, possible to situate a second pressure sensor having the same design on the pressure accumulator and use it for a comparison. German Patent Application No. DE 10 2008 043 592 is an example of a patent publication from this field.